Case studies of three-dimensional effects on the behaviour of test embankments

Abstract

This paper uses both two-dimensional (2D) and three-dimensional (3D) finite element (FE) analyses to examine three cases involving the construction of full-scale test embankments to failure on soft clay deposits. By comparing the calculated fill thickness at failure from 2D and 3D analyses, it is shown that 3D effects are significant for all test fills, despite the dramatically different locations, fill thicknesses, and underlying clay deposits. In addition, the calculated undrained displacement and extent of failure from 3D analysis agree well with those measured in each case. The risk of neglecting 3D effects is highlighted by the analyses, where it is shown that failure to account for 3D effects while interpreting the response of a test embankment can lead to unsatisfactory performance of the actual long embankment. Finally, by comparing FE analysis results with well-known bearing capacity factors, it is shown that test embankments with a base length to width ratio less than 2 are more strongly influenced by 3D effects than spread footings on similar soil profiles. The analyses presented in this paper provide practical insight into some factors that should be taken into account for the design and construction of embankments and test fills on soft clay deposits.